Spectral and cyanide binding properties of the cytochrome aa3 (600 nm) complex from Bacillus subtilis

The cytochrome aa3 (600 nm) complex, or menaquinol oxidase, from Bacillus subtilis is a member of the cytochrome oxidase superfamily of respiratory membrane protein complexes. We have characterized some spectral properties of this enzyme and its reaction with cyanide. The magnetic circular dichroism (MCD) spectrum of the oxidized enzyme has a single band at 1560 nm in the near-infrared region assigned to bis-histidine-ligated, low-spin ferricytochrome a. The other heme, cytochrome a3, is presumably high-spin in the oxidized enzyme, as isolated. The absence of a trough in the MCD spectrum at 790 nm, observed previously with mammalian cytochrome c oxidase and assigned to CuA (Greenwood et al., Biochem. J. 215, 303-316, 1983), is consistent with the absence of this center from the menaquinol oxidase. When the heme ligand cyanide is added to oxidized menaquinol oxidase, a new MCD band appears at 2010 nm, while the band at 1560 nm is unperturbed. The new band is assigned to low-spin ferricytochrome a3 bound with cyanide. The long-wavelength position of this cyanide-induced band is proposed to arise from the close interaction of cytochrome a3 with the copper atom, CuB. The kinetics of cyanide binding to oxidized cytochrome aa3(600 nm) reveal a spectrally simple, yet kinetically complex process. The reaction is biphasic with second-order rate constants of 45 and 0.61 M-1s-1 at 1 mM KCN, with each phase constituting about 50% of the overall reaction. When the enzyme is subjected to a cycle of anaerobic reduction and air oxidation, the subsequent reaction with cyanide occurs in a single phase at the faster rate. This behavior is ascribed to different conformations of the binuclear center exhibiting different reactivities with cyanide, and is in keeping with that previously established for the structurally more complex mitochondrial cytochrome c oxidase. However, the electronic spectral characteristics of some of the species involved in these reactions are different in the present bacterial case from those of reported eukaryotic systems.

Axonal transection in the lesions of multiple sclerosis

BACKGROUND

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system and is the most common cause of neurologic disability in young adults. Despite antiinflammatory or immunosuppressive therapy, most patients have progressive neurologic deterioration that may reflect axonal loss. We conducted pathological studies of brain tissues to define the changes in axons in patients with multiple sclerosis.

METHODS

Brain tissue was obtained at autopsy from 11 patients with multiple sclerosis and 4 subjects without brain disease. Fourteen active multiple-sclerosis lesions, 33 chronic active lesions, and samples of normal-appearing white matter were examined for demyelination, inflammation, and axonal pathologic changes by immunohistochemistry and confocal microscopy. Axonal transection, identified by the presence of terminal axonal ovoids, was detected in all 47 lesions and quantified in 18 lesions.

RESULTS

Transected axons were a consistent feature of the lesions of multiple sclerosis, and their frequency was related to the degree of inflammation within the lesion. The number of transected axons per cubic millimeter of tissue averaged 11,236 in active lesions, 3138 at the hypocellular edges of chronic active lesions, 875 in the hypocellular centers of chronic active lesions, and less than 1 in normal-appearing white matter from the control brains.

CONCLUSIONS

Transected axons are common in the lesions of multiple sclerosis, and axonal transection may be the pathologic correlate of the irreversible neurologic impairment in this disease.

Genomic sequence of a Lyme disease spirochaete, Borrelia burgdorferi

The genome of the bacterium Borrelia burgdorferi B31, the aetiologic agent of Lyme disease, contains a linear chromosome of 910,725 base pairs and at least 17 linear and circular plasmids with a combined size of more than 533,000 base pairs. The chromosome contains 853 genes encoding a basic set of proteins for DNA replication, transcription, translation, solute transport and energy metabolism, but, like Mycoplasma genitalium, it contains no genes for cellular biosynthetic reactions. Because B. burgdorferi and M. genitalium are distantly related eubacteria, we suggest that their limited metabolic capacities reflect convergent evolution by gene loss from more metabolically competent progenitors. Of 430 genes on 11 plasmids, most have no known biological function; 39% of plasmid genes are paralogues that form 47 gene families. The biological significance of the multiple plasmid-encoded genes is not clear, although they may be involved in antigenic variation or immune evasion.

Cerebral venous thrombosis in nephrotic syndrome

This report describes cerebral venous sinus thrombosis, a rare and perhaps under-diagnosed complication of nephrotic syndrome. We review the pathophysiology of the coagulopathy associated with nephrotic syndrome including abrupt renal loss of antithrombin III. We propose a rationale approach to treating this condition with low-molecular-weight heparin and antithrombin III replacement.

CNP overexpression induces aberrant oligodendrocyte membranes and inhibits MBP accumulation and myelin compaction

2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) is highly enriched in myelin-forming cells where it is concentrated at the cytoplasmic side of all surface membranes except those of compact myelin. Previous studies have provided evidence that CNP is functionally involved in migration or expansion of membranes during myelination. This hypothesis is supported, in part, by the production of aberrant myelin membranes in transgenic mice that have a 6-fold increase in CNP expression. In addition, many myelin lamellae in these CNP-overexpressing mice lacked major dense lines (MDLs). The purpose of the present study was to determine if CNP overexpression altered: (1) oligodendrocyte and myelin membrane production during early stages of myelination, and (2) the ultrastructural distribution of CNP and myelin basic protein (MBP) in myelin membranes. We identified aberrant membrane expanses that extended from premyelinating oligodendrocyte processes, the periaxonal membrane, and the contact point between oligodendrocyte processes and myelin internodes. Myelin membranes without MDLs were deficient in MBP and enriched in CNP. These data support a functional role for CNP during oligodendrocyte membrane expansion and indicate, for the first time, that CNP may help target MBP to compact myelin.

Growth and Structure of Zirconium Hydrous Polymers in Aqueous Solutions

Zirconium oxychloride solutions prepared at different pH were heated at elevated temperatures for various aging periods to gain an understanding of the growth mechanism and structure of zirconium hydrous polymers. Small angle X-ray scattering (SAXS) measurements were made on these solutions. It was observed that shape of clusters at the earlier stages of growth is close to a rod rather than a sheet as suggested earlier. The scattering data indicate that a rod-shaped primary particle is formed at pH 1.2, and on an increase in the pH, the primary particles become more branched. On aging more than 1250 min at 92°C, these primary particles form large aggregates while retaining the primary particle structure. These aggregates, which are mass fractal in nature, restructure while growing in size and eventually transform into dense particles. Scattering data in this study were not enough to determine a specific kinetic growth model of the aggregates because the scattering intensity at low q constantly changes with time during the restructuring process. Copyright 1997 Academic Press. Copyright 1997Academic Press

African-American families with chronically ill children: oversights and insights

From a critical review of the literature concerning African-American families' management and care of children having chronic illness, we concluded that information on culture-related experiences in such families remains seriously deficient. To present an accurate picture of African-American life as these families manage a child with a chronic illness, more comprehensive and detailed descriptions of family caregiving styles and other experiences are needed.

Transformation and tumorigenic properties of a mutant polyomavirus containing a middle T antigen defective in Shc binding

Polyomavirus middle T antigen is phosphorylated on several tyrosine residues which act as binding sites for cellular proteins, including phosphatidylinositol 3-kinase, Shc, and phospholipase C-gamma. In this report we describe the transforming properties and tumor-inducing ability of a polyomavirus that contains a single-site mutation in middle T antigen which changes a tyrosine residue at amino acid position 250 to serine. This mutation disrupts the association of middle T with the transforming protein Shc. The mutant virus is weakly transforming, inducing foci which are smaller and of different morphology than those of the wild type. Although the virus induced tumors in close to 100% of inoculated mice, the spectrum of tumors and their morphology were altered compared to those of wild-type virus. The mutant virus induced a reduced frequency of kidney and thymic tumors. Both the mammary gland and the thymic tumors that were induced were histologically distinct from those induced by wild-type polyomavirus. These results demonstrate that the signal transduction pathway that is deregulated by the middle T-Shc association is important for full transformation of cells in culture and for tumor induction in some target tissues in the mouse-polyomavirus system.

Solving the mystery of the Colorado Brown Stain

The life and work of Dr. Frederick S. McKay in solving the mystery of the Colorado Brown Stain changed the objectives of restorative and preventive dentistry. McKay was an intellectually diversified man whose personal interests ranged from economics to opera. Professionally his strong commitment to research led to dedicate thirty years of his life to the search for the mysterious agent that caused the Colorado Brown Stain which mottled but also produced caries-free teeth. His discovery of fluoride in drinking water and its effect on enamel was a critical breakthrough in understanding the etiology and prevention of dental caries. This discovery is the foundation for water fluoridation which is the single most effective public health measure to inhibit tooth decay.

Effects of pramlintide, an analog of human amylin, on plasma glucose profiles in patients with IDDM: results of a multicenter trial

The effects of subcutaneous administration of 10, 30, or 100 microg q.i.d. pramlintide, an analog of human amylin, on plasma glucose regulation in patients with IDDM were evaluated in a multicenter trial. The plasma glucose response to a Sustacal test meal was significantly reduced compared with placebo both after 1 week and after 2 weeks of administration of 30 or 100 microg pramlintide. In addition, 24-h mean plasma glucose concentrations were significantly lowered in patients receiving 30 microg of pramlintide for 2 weeks compared with placebo, while the 100-microg pramlintide dose did not reach statistical significance for the 24-h glucose profiles. At 10 microg, pramlintide had no effect on the 24-h glucose profile or on the plasma glucose response to a Sustacal test meal. The reduction in 24-h glucose concentrations and glucose concentrations after the Sustacal test meal observed at the 30-microg pramlintide dose was not accompanied by an increased incidence of hypoglycemic events. The most frequent adverse events were dose-related and involved transient upper gastrointestinal symptoms. A majority (>80%) of the patients who reported these adverse events during week 1 did not report them in week 2. These data indicate that pramlintide effectively reduces plasma glucose concentrations as reflected in both a 24-h glucose profile and a Sustacal test meal while maintaining an acceptable safety profile.

Resolution of CNS lesions following treatment of experimental allergic encephalomyelitis in macaques with monoclonal antibody to the CD18 leukocyte integrin

Experimental allergic encephalomyelitis (EAE) in macaques is an acute inflammatory and demyelinating disease of the central nervous system (CNS) which has been studied extensively as a model of the human demyelinating disease multiple sclerosis (MS). The in vivo administration of monoclonal antibodies against CD18, the common beta-chain of a leukocyte integrin, at the onset of clinical disease, significantly prolonged the survival of nine of 11 macaques (82%) and in some cases completely reversed the clinical appearance of disease. Treatment with anti-CD18 mAbs dramatically reduced the extent of inflammation in brain lesions as determined by magnetic resonance imaging (MRI). These improvements confirm that anti-CD18 mAbs are powerful anti-inflammatory agents in vivo and suggest that such mAbs may provide effective treatment of both demyelinating and inflammatory CNS diseases in man.

Portal venous thrombosis in a backpacker: the role of exercise

Effort thrombosis usually afflicts an extremity and is caused by compression. This case report, in contrast, involves superior mesenteric and left portal vein septic thrombosis in a backpacker following prolonged hiking and abdominal straining. The condition may have been caused by localized splanchnic venous ischemia, erosion of the bowel-blood barrier, and release of bacterial endotoxin in this dehydrated and detrained athlete. Diagnosis of this disorder is aided by noting characteristic abdominal pain, fever, nausea, and vomiting, as well as by imaging with MRI, CT, or duplex ultrasonography. Antibiotics and anticoagulants are key to treatment.

Lifespan and lesions in genetically heterogeneous (four-way cross) mice: a new model for aging research

Genetically heterogeneous animal models provide many advantages for research on aging but have been used infrequently. We present here lifespan and lesion data from a study of mice bred as a cross between (AKR/J x DBA/2J)F1 females and (C57BL/6J x SJL/J)F1 males. In such a four-way cross population, each mouse is genetically unique, but replicate populations of essentially similar genetic structure can be generated quickly, at low cost, and of arbitrary size from commercially available, genetically stable hybrid parents. We employed a protocol in which mice judged to be severely ill were euthanatized to obtain tissue in optimal condition for necropsy, and we were able to infer a likely cause of illness in 42 of 44 animals. Malignant lymphoma, including at least four histopathologically distinct subtypes, was the most common cause and was also a frequent incidental finding in mice dying of other causes. Neoplastic disease, benign or malignant, was the sole or a contributing cause of illness in 90% of the mice for which a cause could plausibly be assigned. A wide range of lethal and nonlethal degenerative lesions was also noted. The coefficient of variation for lifespan in these genetically heterogeneous mice was 26%, similar to that seen in analyses of recombinant inbred mouse lines. Baseline lifespan and pathology data on four-way cross mice is a useful prelude to the exploitation of this rodent model in tests of genetic and mechanistic hypotheses about aging.

Continuous quality improvement can improve glycemic control for HMO patients with diabetes

OBJECTIVE

To evaluate the impact of a continuous quality improvement (CQI) intervention on glycemic control of patients with diabetes mellitus attending a primary care clinic.

METHODS

A CQI process designed by the Minnesota Department of Health to improve diabetes care was implemented at a volunteer clinic, with another similar clinic not using the CQI process assessed for comparison. Adults with diabetes were identified at both clinics using diagnostic and pharmacy databases. Glycosylated hemoglobin (HbA1c) values (reference range, 4.3%-6.1%) and out-patient utilization and charges were compared for all patients with diabetes at each clinic for the 12 months before and 18 months after initiation of the CQI intervention.

RESULTS

The mean HbA1c value at the intervention clinic fell from 8.9% at baseline to 8.4% at 12 months and to 7.9% at 18 months. The mean HbA1c value at the comparison clinic was 8.9% at baseline, 8.9% at 12 months, and 8.8% at 18 months (difference between clinics, t = 4.13, P < .001). Differences after the intervention in the proportion of patients at the comparison clinic (n = 121) vs the intervention clinic (n = 122) with HbA1c values of 8% or less (40% vs 51%), between 8% and 10% (33% vs 37%), and 10% or greater (27% vs 12%) were unlikely due to chance (chi 2 = 9.7, 2 df, P = .008). The intervention was not associated with increased utilization of outpatient visits or outpatient charges.

CONCLUSIONS

Involvement of nurses, physicians, and managers in a CQI process can improve patients' glycemic control in some health maintenance organization primary care settings, without increasing utilization or charges. Health maintenance organizations should consider CQI as one possible method to improve diabetes outcomes.

Empirical techniques for determining the reliability, magnitude, and pattern of neuropsychological change after epilepsy surgery

PURPOSE

We assessed test-retest neuropsychological performance in patients with complex partial seizures to derive reliable change indices (RCIs) and regression-based norms for change, indices that may be helpful in assessing cognitive outcome after anterior temporal lobectomy.

METHODS

Forty patients with complex partial seizures (CPS) who did not undergo epilepsy surgery were administered a comprehensive neuropsychological battery on two occasions. Their test-retest data were used to compute both RCIs and regression-based norms for change for each neuropsychological index. RCIs corrected for practice effects provide a confidence interval (CI) indicating the degree of performance change required to exceed the variability attributable to sources of error (e.g., practice, test-retest reliability). Regression-based norms for change also correct for several sources of measurement error and examine observed versus expected test-retest changes on a common metric, thereby facilitating determination of the degree and relative magnitude of change across cognitive domains.

RESULTS

Mean changes in test-retest performance were generally modest, but were evident across several test measures. Our data indicate a considerable degree of individual variability in test-retest performance.

CONCLUSIONS

RCIs and regression-based norms are complementary indexes and can be particularly useful in examining the test-retest performance of individual patients who undergo epilepsy surgery as well as in the more general investigation of cognitive outcome after epilepsy surgery.

Safety of commercial air travel following myocardial infarction

BACKGROUND

Travelers occasionally suffer myocardial infarction (MI) while abroad. Existing guidelines recommend a 4- to 24-week convalescent period following MI before air travel should be permitted.

HYPOTHESIS

Air travel may be undertaken safely in the early post-MI period.

METHODS

The aeromedical transport records of two international medical assistance companies over a 3-yr period were reviewed. We identified 209 patients who suffered MI; 13 transported by private air ambulance were excluded. We reviewed the aeromedical transports of the remaining 196 adults carried on commercial aircraft between 3-53 d post-MI to investigate the safety of air travel in this group. Data were recorded regarding patient age; sex; location of MI; complications of MI; presence of medical escort; duration of flight(s); use of oxygen, medications, or cardiac monitoring during transport; and development of symptoms in flight.

RESULTS

Within 7 d of their acute MI 3 patients (2%) were transported; 87 (44%) between days 8-14 post-MI; 65 (33%) between days 15-21; 27 (14%) between days 22-28; and 14 (7%) more than 28 d post-MI. Some 187 patients (95%) were transported without incident; 9 (5%) patients experienced symptoms requiring evaluation by the escorting physician. Of the 9, 6 problems occurred in patients being transported less than 14 d post-MI. Symptoms resolved spontaneously or immediately after physician intervention in all but one case.

CONCLUSION

International aeromedical transport of patients may be safely accomplished 2-3 wk after an acute MI when an accompanying physician is present. Recommendations for delaying travel more than 4 wk after infarction are not supported by clinical experience and should be revised.

A carbon monoxide irreducible form of cytochrome c oxidase and other unusual properties of the "monomeric" shark enzyme

Contrary to previous reports, the functional and spectral properties of "monomeric" shark cytochrome c oxidases are not entirely similar to those of the "dimeric" beef enzyme. Most significantly, unlike the behavior of beef oxidase, the fully oxidized shark enzyme is not reducible by carbon monoxide. Also, preparations of the shark enzyme, isolated at pH 7.8-8.0, lead to more than 60% of the sample always being obtained in a resting form, whereas similarly prepared beef oxidase is very often obtained, both by ourselves and others, exclusively in the pulsed form. Although the electronic absorption, magnetic circular dichroism and electron paramagnetic resonance (EPR) spectra of cytochrome c oxidase obtained from several shark species are similar to those of the beef enzyme, there are some significant differences. In particular, the Soret maximum is at 422 nm in the case of the fully oxidized resting shark oxidases at physiological pH and not 418 nm as commonly found for the beef enzyme. Moreover, the resting shark oxidases do not necessarily exhibit a "g = 12" signal in their EPR spectra. The turnover numbers of recent preparations of the shark enzyme are higher than previously reported and, interestingly, do not differ within experimental uncertainty from those documented for several beef isoenzymes assayed under comparable conditions.